As electronic devices become smaller, the density of electronic components and traces on internal circuit boards increases. Due to this increased density, many circuit boards and modules are encapsulated using a resin designed to protect electronic components from foreign objects, increase reliability, and enable further processing (such as conformal RF shielding). Various methods of encapsulation have been implemented in the electronics industry, including potting, transfer molding, injection molding, conformal coating, and the like.
However, some circuit board designs can be incompatible with standard encapsulation techniques and materials. For example, optical components such as light emitting diodes (LEDs), photo diodes, and ambient light sensors can be rendered unusable when covered by opaque encapsulants along axes of operation. In addition, many conventionally used encapsulants can act as a thermal insulator, restricting the ability of components to disperse heat. Furthermore, encapsulation in certain areas can hinder the ability to form electrical connections between the circuit board and other components or perform rework on an area of the circuit board.
Therefore, what is desired is a way to selectively encapsulate a circuit board such that certain areas can benefit from the encapsulation while other areas can be without an encapsulation layer or can allow optical signals, electrical signals, and thermal energy to pass through the encapsulation layer.